Pete Aldridge, undersecretary of defense for acquisition, technology and logistics, and Alan Williams, the assistant deputy minister for materiel, signed the agreement in a Pentagon ceremony.

Under the agreement, Canada will provide $150 million over the next 10 years for the system development and demonstration phase of the JSF program. Canada was also part of the concept demonstration phase from 1996 to 2001.

"We in the United States government treasure our relationship with our neighbor to the north," Aldridge said. "This is yet another example of our cooperative relationship across so many different programs. Our cooperation effort on Joint Strike Fighter will reinforce a longstanding and close relationship between our two countries and will serve to strengthen the interoperability of our industrial base."

Williams said the agreement would give Canada a window into the leading edge technologies being developed in the JSF.

"Canada's decision to participate in the JSF program is yet another clear demonstration of the Canadian government's continuing commitment to North American security and industrial cooperation," Williams said.

Lockheed-Martin leads the JSF team, which includes Northrop Grumman and British Aerospace.

There are three variants of the JSF. The Air Force's F-35A version is a conventional takeoff and landing airplane to replace the F-16 Falcon and A-10 Thunderbolt II. It will partner with the F-22 Raptor. The Air Force plans to buy 1,763 of the aircraft.

The Navy's F-35B is a carrier-based strike fighter to complement the F/A-18E/F Super Hornet. It will replace earlier versions of the F/A-18 as well as the A-6 Intruder, which already has left the inventory. The Navy plans to purchase 480 JSF aircraft.

The Marine Corps, Royal Navy and Royal Air Force need and want a short takeoff and vertical landing aircraft, dubbed the F-35C. The Marines want 609 of the new aircraft to replace their AV-8B Harriers and F/A-18 Hornets. The British want 150 to replace Sea Harriers and Tornado fighters.

Canada currently flies the CF-18 and plans on keeping them through 2017. The Canadians will assess their needs and decide which variant they need by then, Williams said.

Aldridge said the Netherlands, Italy, Norway, Denmark and Turkey have also expressed interest in the JSF.